[ni.el.lo] n, pl ni.el.li or niellos [It, fr. ML nigellum, fr. neut. of L nigellus blackish, dim. of niger black] (1816) 1: any of several black enamel-like alloys usu. of sulfur with silver, copper, and lead
2: the art or process of decorating metal with incised designs filled with niello
3: a piece of metal or an object decorated with niello
[2]niello vt (1866): to inlay or ornament with niello